It is notoriously well known in the art that the provision of a shoulder belt in a vehicle occupant restraint system significantly increases the system's ability to restrain movement of the occupant in the event of a sudden vehicle maneuver or collision. There are, however, certain vehicle seating arrangements which do not easily lend themselves to the provision of a shoulder belt, such as the arrangement of driver and/or passenger seats in a commercial vehicle and, in particular, to the driver's seat in a bus.
As illustrated schematically in FIG. 1, a vehicle 10 includes a seat 12 (such as a driver's seat) that is mounted to the vehicle floor 14 (for the purposes of the present description, the vehicle floor and/or chassis is designated as ground and is therefore a fixed reference plane for the occupant restraint system). A driver (or passenger) 16 occupies the seat 12. A distal end of a shoulder belt (not shown) of an occupant restraint system is attached to a releasably attachment point 18 that is in turn anchored to the floor 14.
The desired trajectory of the shoulder belt after coupling to attachment point 18 is indicated by the dashed line 20. When in this position, the shoulder belt will lay across the occupant's chest, which is the most comfortable position. Unfortunately, many vehiclees 10 have windows 22 that are positioned at the desired point of attachment of the proximal end of the shoulder belt to the vehicle 10 sidewall when the shoulder belt position is as shown at 20. Obviously, the proximal end of the shoulder belt cannot be mounted to the window.
One easy solution known in the prior art is to simply move the mounting position of the proximal end of the shoulder belt to a location 24 above the window 22, where the shoulder belt can be securely anchored to the sidewall of the vehicle 10. While this solution provides a secure attachment point for the proximal end of the shoulder belt, it forces the shoulder belt to follow a trajectory indicated by the dashed line 26. Such a trajectory 26 is undesirable in that it moves the shoulder belt away from the chest of occupant 16. The trajectory 26 is very uncomfortable to the occupant 16, who will in response to this discomfort often slide the shoulder belt under his arm (thereby severely decreasing its effectiveness) or simply not use the restraint system at all.
A prior art occupant restraint system which attempts to solve the difficulties illustrated in FIG. 1 is illustrated schematically in FIG. 2 and indicated generally at 30. The restraint system 30 includes a shoulder belt 32 with a tongue 34 sliding thereon for releasable engagement with the attachment point 18. The webbing of the shoulder belt 32 is routed through the lower half of a D-ring 36 and terminates in an emergency locking retractor (ELR) 38 mounted to the floor 14. The D-ring 36 is supported through its upper-half by a webbing section 40 that includes a loop at each end. The D-ring 36 is captured within the distal loop of the web 40, while the proximal loop thereof engages the distal end of a slack adjuster 42.
The proximal end of slack adjustor 42 has a length of webbing 43 looped therethrough. A first end 44 of the webbing 43 is routed through the lower half of a second D-ring 46 and then anchored to the floor 14 through a second slack adjustor 48. The first end 44 is sewn together at 49 in order to prevent sliding through D-ring 46. The D-ring 46 is mounted to the sidewall or ceiling of the vehicle by means of the bracket 48 and bolt 50. A second end 52 of the webbing 43 is also routed through the lower half of D-ring 46 and terminates in a loop 54. Finally, a plastic sleeve 56 captures the webbing 40, the first end 44 and the second end 52 therein.
In operation, the occupant restraint system 30 of FIG. 2 is mounted between the vehicle floor (or to the wall or seat near the floor) and the upper sidewall or ceiling. The slack adjustor 48 is then adjusted in order to make the first end 44 of the web 43 taut between the floor 14 and the D-ring 46. Once thus configured, the height of the D-ring 36 from the floor 14, and hence the trajectory of the shoulder belt 32 across the occupant of the seat 12, may be adjusted as follows: In order to raise the height of the D-ring 36 above the floor 14, a finger is inserted through the loop 54 and the loop 54 is pulled in a downward direction, thus raising slack adjustor 42 and hence D-ring 36. In order to lower the D-ring 36, the slack adjustor 42 must be tilted inboard and moved downward, thus lowering D-ring 36.
Although the prior art occupant restraint system 30 of FIG. 2 allows for adjustment of the height of the D-ring 36 (and therefore the trajectory of the shoulder belt 32 across the occupant of the set 12), it suffers from several drawbacks. First, it is a rather complicated device to manufacture, install and use, due to its high parts count and complex webbing routings. Secondly, it is not intuitively obvious how to adjust the height of the D-ring 36 without training, as portions of the device must be pulled downward regardless of whether the D-ring 36 is to be moved downward or upward. Finally, breakage of the relatively fragile plastic sleeve 56 will allow the shoulder belt pivot point to shift from the D-ring 36 to the D-ring 46, placing the shoulder belt 32 at an improper trajectory with respect to the occupant of the seat 12.
There is therefore a need for an occupant restraint system for a vehicle (such as a vehicle) which allows the upper pivot point for the shoulder belt to be located adjacent a window (or other location where it is undesirable or impossible to mount a pivot mechanism), that is relatively simple to manufacture and install and that is intuitive in the operation of its height adjustment. The present invention is directed toward meeting these needs.